VOLUME 50, ISSUE 2/2009

Particleboards are of enormous relevance for the European furniture industry. Due to the growing competition on round wood with the sawmill industry, the producers of groundwood pulp, pulp and pellets and with the thermal utilization of wood, the wood-based industries show increasing interest in alternative raw materials. At the moment, a few companies are producing particleboards made of hemp shives in Germany. The aim of a European joint project was to develop lightweight flat-press particleboards for the furniture industry made from residues of agricultural plants. The stalks of sunflower (Helianthus annuus), topinambur (Helianthus tuberosus), maize (Zea mays) and miscanthus (Miscanthus sinensis giganteus) are characterized by very lightweight pith parenchyma, which makes it particularly suitable for the production of lightweight particleboards. In contrast to wheat, barley, rye and rape the cultivation of sunflower, topinambur and miscanthus is not widespread in Germany. The cultivated areas used for flax as well as for hemp were reduced drastically during the last years. Further considerations which have to be taken into account regarding the availability of agricultural raw materials like the harvest per area under cultivation, the crop loss due to harvesting and conditioning as well as miscellaneous types of use will be described.

It is possible to characterize the sequence of the annual ring widths over average value and standard deviation because the sequence is normal distributed. We find only very weak correlations between these two characteristics and the most important elastic properties of wood: density, modulus of elasticity and damping. This agrees with already 1984 of Holz expressed assumptions [1]. A connection with acoustic characteristics of guitars manufactured from the examined resonance wood samples could not be determined. Also a subjective investigation of the resonance wood samples was included by instrument maker.

The analysis of the pattern of annual growth rings is done by a lot of different disciplines: Phytology, wood biology, climatology, pollution control, geography, ecology, archaeology, architecture, science of forestry etc. But the machining of cross-grained wood is one of the most difficult grinding tasks in woodworking. Up to now, such tree discs are prepared with a special machine, which cuts the surface with a sharp blade. This solution is very expensive, because for every test specimen a new blade is required. Furthermore it is just possible to prepare a small stripe instead of the whole disc. With the machining process of turn-milling it is possible to finish such tree discs in an adequate quality and in a short cutting time. After the milling strategy and the test equipment were presented in the first part, the second part will discuss the experiment parameters and the results.

In this study, the relationship between wet bending strength and wet transverse tensile strength of Oriented Strand Boards (OSB) and particle boards (PB) is investigated. The need for research derives from the problem of stress development in the tensile test specimen possibly occurring during wet pre-treatment according to EN 1087-1 and causing pre-existing defects of the composite prior to the actual strength testing. The wet bending strength presents an alternative test method and offers advantages in test handling as there is no need for gluing on test yokes for load transmission. Insofar as a correlation between the values of wet bending strength and wet transverse tensile strength exists, the wet bending strength test could present a suitable method for the evaluation of the composite after wet storage. The results are separated into board types and are shown and discussed in two parts (OSB part 1 and PB part 2). The relationship between the test methods with wet and dry specimens is proven by very good correlation coefficients in case of transverse tensile strength and bending strength of OSB. Predominantly above-average strict correlations have also been determined when comparing transverse tensile strength and bending strength of OSB.

An alternative method to quantify the wood failure percentage on shear test specimens was developed, experimentally tested and successfully applied to specimens with different wood adhesive combinations. This method consists of a staining technique for a better differentiation of wood and adhesive in terms of colour, and an image-processing step for an estimation of these colour-differentiable surfaces. The new method allows a more objective determination of the wood failure percentage and enables an assessment of the failure mode based on the pattern of the coloured fracture surfaces.

Certain extractives from thermally modified beech have fungicidal properties. Methanol extracts, resolubilized in propanone, caused a significant retardation of fungal growth on native beech specimen. Beech specimen impregnated with these extractives could be assigned to the durability class 4, i. e. not permanent. Other extracts of thermally modified beech, in particular water extracts, did not show significant improvement in resistance. The analysis of methanol extracts using gas chromatography coupled with mass spectrometry (GC-MS) showed an increased amount of phenolic compounds known to increase resistance. Their presence in organic extracts of thermally modified wood may explain the improvement of the resistance of the impregnated specimen.

Wood Plastic Composites (WPC) have been used for several years as complex composite materials in a wide range of applications. The development is based on the availability of new fields and products. Most raw material supplier’s offer optimized products for the production of WPC e. g. special pre processed wood fibers and optimized additives. These optimized raw materials can achieve a higher property level and better characteristics, as well as optimized products for its field of use. The first part of this article gives an overview about the main characteristics and properties of the raw materials for WPC (wood, plastic and additives). WPC formulations are mainly based on Polyethylene, Polypropylene and Polyvinylchloride. Therefore, this article will focus on the processing properties and usage properties of this three matrix types. Functional principle, mode of action, advocacies of types and percentage of additives for WPC, e. g. coupling agent, lubricants, thermo and UV-stabilizers as well as colours and parting agents will be explained.

Scaffoldings were made from wood all times. For modern scaffoldings, metals and polymer materials are increasingly used. However, timber and wood-based materials are efficient and widely-used in scaffolding work. The several materials have their specific advantages and disadvantages. Due to the high number of industrial injuries caused by the failure of working platforms, a continuous inspection of the scaffolding elements is required. Within the framework of the research project, various influences on the serviceability were tested and conclusions for the inspection of the elements were drawn. It could be evidenced that solid wood and wood-based materials may be used for secure platforms of scaffolds in case of professional material selection and maintenance. Research projects will be proceeded in this scope of range also in the future.